Countdown button angularjs

i created a countdown feature where it only counts if the user is in the current window of the browser, and it works very well, the only problem is when i insert my code in angularjs controller. It stops working, above i leave my code to everybody have a idea what is wrong.

js:

var span = angular.element('#count');
        var counter = 30;
        var timer;

        var startTimer = function() {
            // do nothing if timer is already running
            if (timer) return;

            timer = setInterval(function() {
                counter--;
                if (counter >= 0) {
                    span.innerHTML = counter;
                }
                // Display 'counter' wherever you want to display it.
                if (counter === 0) {
                    alert('this is where it happens');
                    stopTimer();
                }
            }, 1000);
        };

        var stopTimer = function() {
            clearInterval(timer);
            timer = null;
        };

        var onBlur = function() {
            stopTimer();
        };

        var onFocus = function() {
            startTimer();
        };

        var onLoad = function() {
            startTimer();
        };


        angular.element(window).load(onLoad);
        angular.element(window).blur(onBlur);
        angular.element(window).focus(onFocus);

html:

<a  class="btn btn-medium btn-orange" href="">
            In<span id="count">30</span></a>